Besides, TS question is so very vague. No proper example or scenario to give an opinion. Most of the time, you should be concerned on the background. If they see you are concerned, they will approach you when they are ready. But they will push you away the moment you become pushy and busy body.

At the end of the day, it is your method of approach that will lead that person to believe you are actually concerned or just plain busy body. And pretty or not pretty girls should not make a difference at all if you are a true friend.

I can tell from your line of questioning, you are only concerned/busy body because she's pretty. No sincerity.